The exemplary embodiments of present invention relate generally to an orthopedic instrument and, more specifically, to an acetabular cup extractor.
In performing hip orthoplasty surgery, an acetabular cup implant is installed in the hip socket or acetabulum. When installing the acetabular cup implant into the acetabulum, bone is removed from the acetabulum to receive the acetabular cup implant and the acetabular cup implant is attached, e.g., with cement, bone screws or press-fitted. The acetabular cup implant may have a porous, typically metal coating shell which surrounds a liner adapted to receive the ball-like head of a hip stem implant. Bone gradually grows onto and/or into the porous metal shell to permanently affix the acetabular cup implant to the acetabulum.
Prosthetic hip joints, like their natural counterparts, experience wear over time. When a prosthetic hip joint becomes worn or damaged to a point necessitating maintenance or replacement, the acetabular cup implant may have to be replaced. In order to replace the acetabular cup implant, an extractor is used to extract the existing acetabular cup implant from the acetabulum.
Among the disadvantages of conventional extractors is that the blades are either permanently attached to the handle or attached with a threaded fastener which actions may prolong surgery time. Conventional extractors have blades with flat cutting edges which require substantial force to plunge the blades into the bone surrounding the acetabular cup implant being extracted. Handles of typical extractors also are not ergonomically shaped which render them uncomfortable to the user because of the substantial force that must be applied to the handle during use. Conventional extractors also typically have a single impact surface to dislodge the blade in the event it gets stuck in the bone, which may not be optimally positioned for striking.
In addition, in conventional extraction systems having a spherical head that caps an implant the spherical head can easily separate from the acetabular cup liner when the handle is used to drive the blade into bone, e.g., by being struck by a hammer. Such separation of the spherical head detrimentally impacts the user's ability to control the point of insertion of the blade into bone. As a consequence, the blade may make an irregular cut of the surrounding bone whereby more bone than necessary may be cut in order to extract the acetabular cup from the acetabulum. In revision surgery to remove existing implants, as little bone as possible should be removed from around the acetabular cup in order to preserve the integrity of the surrounding bone.